Pro-gay marriage stories outnumbered anti-gay marriage stories by five-to-one in a new study of coverage of the debate released Monday by the Pew Research Center Project for Excellence in Journalism.

And we’re not talking here about subtly inflected coverage. To qualify as “biased” in the Pew study, stories had to feature at least twice as many comments in support of same-sex marriage as against it.

When asked if the results supported conservative claims of liberal bias in journalism, Pew’s Amy Mitchell demurred. “I don’t think the study can necessarily speak to that one way or another,” said Ms. Mitchell, acting director of the project.

Pew interpreted its results as largely a reflection of the fact that the relevant stories happened to be, according to the Associated Press, “about polls showing societal attitudes swiftly moving toward support for gay marriage, or about politicians announcing their support.”

In other words, while story selection might have been biased, that’s not media bias. That’s … something else.

Of course, while polls have shifted in favor of same-sex marriage, the public now favors it, according to Pew’s own findings, by 51%-42% — which some are sure to notice is a ratio of roughly five-to-four, not five-to-one like the ratio of stories theoretically dictated by the level of public approval.

“Certainly it is evident in these findings the degree to which supporters of same-sex marriage were largely successful in getting their message out in a clear way, a consistent way, across a wide swath of the news media,” said Ms. Mitchell.

But, strangely enough, same-sex marriage supporters weren’t nearly as successful getting their message across through social media, like Twitter, where public opinion expresses itself directly, unmediated by journalistic gatekeepers. Tweets, according to the study, split about evenly between pro and con.

Even at Fox News, stories favoring gay marriage far outnumbered those opposing it — by an almost four-to-one margin (29%-8%). The rest of Fox’s stories (63%) reflected — dare we say it? — a fair and balanced split between supporters and opponents.

The Pew survey was conducted during a two-month window starting just before the Supreme Court began hearing arguments in late March on the federal Defense of Marriage Act and California’s Proposition 8.